This invention relates to a cyclohexane derivative used as a component of liquid crystal materials and a composition containing the same.
Display devices which liquid crystals are applied thereto utilize an electro-optic effect based on the anisotropies of the dielectric constant and the electric conductivity of liquid crystal substances. Liquid crystal display modes include various ones such as dynamic scattering mode, twist nematic mode, phase transition mode, DAP mode, guest-host mode, etc. Properties required for liquid crystal substances used for liquid crystal display vary depending on the respective liquid crystal display modes, and a broad mesomorphic range, stabilities to moisture, air, light, heat, electricity, etc., and others and commonly required for any display modes. Further, it is also desired that when liquid crystal substances are used for liquid crystal display devices, the resulting display elements have a short response time and can be driven under a voltage as low as possible. At present, however, there is no single compound which satisfies all of these requirements, but practically, liquid crystalline mixtures obtained by mixing compound(s) similar to liquid crystal compounds with several kinds of liquid crystal compounds have been used.
Recently, as the use applications of liquid crystal displays have been enlarged, specific features required for liquid crystal materials have also become severer. For example, as seen in the case of on-vehicle displays where the service temperature range is in the range of -40.degree. to +100.degree. C., liquid crystal materials for low temperatures have also been desired.
As compounds having similar substituents on a terminal phenyl ring thereof to those of the compound of the present invention mentioned later, compounds expressed by the following formulas (1) or (2) are disclosed in Japanese patent application laid-open No.sho 61-501920/1986 (International patent application No. PCT/EP 85-00163, International publication No. WO 85/04874); and compounds expressed by the following formulas (3) or (4) are disclosed in U.S. Pat. No. 4,551,264: ##STR2##
Further, a compound of the formula (I) wherein l=1 and m=0 is disclosed in Japanese patent application laid-open No. Sho 62-103057/1987, but this compound is somewhat inferior in the liquid crystal properties and moreover it has a high viscosity for a two-rings compound. Comparison of these compounds with the compound of the present invention will be shown in comparative test mentioned later.